The goal of this Mentored Patient-Oriented Research Career Development Award (K23) is to prepare Dr. Bagner for an independent clinical research career focused on developing preventive interventions for infants and their families. Dr. Bagner's long-term career goals are to develop a transdiciplinary research program examining effective interventions for infants at risk for externalizing behavior problems and help advance evidence-based practice for infants with other behavioral and emotional problems. In the context of the K23 training plan, Dr. Bagner's short-term training goals are to: (1) acquire specialized training in the unique processes of infant development, including typical and at-risk populations, and the nature of relationship-based interventions; (2) gain knowledge and expertise in the design, execution, and analysis of conducting home- based prevention trials with infants and their families; and (3) broaden understanding of ethical and multicultural issues relevant to conducting intervention research with low-income families. This training plan will be facilitated by: (a) expert mentorship from Drs. Wendy Silverman, Barry Lester, David Olds, Lorraine Bahrick, Alice Carter, James Jaccard, William Pelham, and Jose Rosa-Olivares; (b) formal coursework and seminars; (c) directed readings; (d) focused clinical experiences in the area of infant mental health; (e) the diverse resources available at Florida International University and Miami Children's Hospital; and (f) implementation of the proposed research project. Dr. Bagner will implement a 5-year research study in which he will develop and evaluate the potential efficacy of a preventive intervention for infants at risk for externalizing behavior problems. The intervention will be an adaptation of Parent-Child Interaction Therapy for use with infants in the home setting (i.e., PCIT-I). The first 18 months of the proposed award will be devoted to developing PCIT-I and piloting it in an open trial. Subsequently, Dr. Bagner will conduct a small randomized trial comparing PCIT-I to standard care. Data concerning the feasibility and acceptability of PCIT-I and clinical significance of findings, combined with results from statistical analyses, will be used to inform an R01 application for a stage II clinical trial.